# nditerIndices
> Create an iterator which returns indices for use indexing into an [`ndarray`][@stdlib/ndarray/ctor] having a specified shape.
## Usage
```javascript
var nditerIndices = require( '@stdlib/ndarray/iter/indices' );
```
#### nditerIndices( shape\[, options] )
Returns an iterator which returns indices for use indexing into an [`ndarray`][@stdlib/ndarray/ctor] having a specified `shape`.
```javascript
var array = require( '@stdlib/ndarray/array' );
var x = array( [ [ [ 1, 2 ], [ 3, 4 ] ], [ [ 5, 6 ], [ 7, 8 ] ] ] );
// returns
var iter = nditerIndices( x.shape );
var v = iter.next().value;
// returns [ 0, 0, 0 ]
v = iter.next().value;
// returns [ 0, 0, 1 ]
v = iter.next().value;
// returns [ 0, 1, 0 ]
// ...
```
The function accepts the following `options`:
- **order**: index iteration order. By default, the returned [iterator][mdn-iterator-protocol] iterates over the last dimensions first, thus corresponding to iteration over contiguous data stored in row-major order. Must be either `'row-major'` or `'column-major'`.
By default, the iterator returns indices such that the last dimensions are iterated over first. To return indices according to a specified order, set the `order` option.
```javascript
var array = require( '@stdlib/ndarray/array' );
var x = array( [ [ [ 1, 2 ], [ 3, 4 ] ], [ [ 5, 6 ], [ 7, 8 ] ] ], {
'order': 'row-major'
});
// returns
var iter = nditerIndices( x.shape, {
'order': 'column-major'
});
var v = iter.next().value;
// returns [ 0, 0, 0 ]
v = iter.next().value;
// returns [ 1, 0, 0 ]
v = iter.next().value;
// returns [ 0, 1, 0 ]
// ...
```
The returned [iterator][mdn-iterator-protocol] protocol-compliant object has the following properties:
- **next**: function which returns an [iterator][mdn-iterator-protocol] protocol-compliant object containing the next iterated value (if one exists) assigned to a `value` property and a `done` property having a `boolean` value indicating whether the [iterator][mdn-iterator-protocol] is finished.
- **return**: function which closes an [iterator][mdn-iterator-protocol] and returns a single (optional) argument in an [iterator][mdn-iterator-protocol] protocol-compliant object.
## Notes
- If an environment supports `Symbol.iterator`, the returned iterator is iterable.
## Examples
```javascript
var array = require( '@stdlib/ndarray/array' );
var zeroTo = require( '@stdlib/array/base/zero-to' );
var nditerIndices = require( '@stdlib/ndarray/iter/indices' );
// Define an input array:
var x = array( zeroTo( 27 ), {
'shape': [ 3, 3, 3 ]
});
// Create an iterator for generating indices:
var it = nditerIndices( x.shape );
// Perform manual iteration...
var v;
while ( true ) {
v = it.next();
if ( v.done ) {
break;
}
console.log( x.get.apply( x, v.value ) );
}
```
[mdn-iterator-protocol]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol
[@stdlib/ndarray/ctor]: https://github.com/stdlib-js/ndarray/tree/main/ctor
[@stdlib/ndarray/iter/entries]: https://github.com/stdlib-js/ndarray/tree/main/iter/entries
[@stdlib/ndarray/iter/values]: https://github.com/stdlib-js/ndarray/tree/main/iter/values